Metadata elements are individual parts, but not necessarily the smallest parts of a metadata structure. They define a particular characteristic to be described. A characteristic can sometimes be sub-divided, thus creating "sub-elements" in IMS metadata, and "qualifiers" in Dublin Core.

The way in which a characteristic or division of that characteristic is to be described is defined by an "attribute" in the IMS/IEEE schemas, and by an "encoding scheme", which is a different type of "qualifier" in Dublin Core.